Yellowstone National Park

Yellowstone National Park

Mark Ralston, AFP/Getty Images

Distance from Baltimore: About a six-hour flight, with stop, to Jackson, Wyo. (56 miles south of Yellowstone) Why it's cool: Winter is the best time to see the wildlife. Yellowstone is home to the largest concentration of mammals in the contiguous 48 states. The park, more than 130 years old

Distance from Baltimore: About a six-hour flight, with stop, to Jackson, Wyo. (56 miles south of Yellowstone) Why it's cool: Winter is the best time to see the wildlife. Yellowstone is home to the largest concentration of mammals in the contiguous 48 states. The park, more than 130 years old (Mark Ralston, AFP/Getty Images)

Distance from Baltimore: About a six-hour flight, with stop, to Jackson, Wyo. (56 miles south of Yellowstone) Why it's cool: Winter is the best time to see the wildlife. Yellowstone is home to the largest concentration of mammals in the contiguous 48 states. The park, more than 130 years oldMark Ralston, AFP/Getty Images